It has become fashionable to watch a video or an image on an electronic device such as a cell-phone or a tablet computer. Since the electronic device such as the cell-phone or the tablet computer has a screen with small area, a content displayed on the electronic device cannot be watched by multiple users at the same time due to such a limitation from the screen of the electronic device. To enable multiple users to watch the content displayed on the electronic device at the same time, the electronic device may be connected to a projector, to project the content displayed on the electronic device via the projector, so that the content displayed on the electronic device can be watched by multiple users at the same time. However, since the projector is unsuitable for movement and not provided in most families, multiple users can only watch the content displayed on the electronic device in turn, thereby causing inconveniences in watching.